Manifold-pressure type metering control



Aug. 16, 1949. 5. J. SHAMES ET AL MANIFOLD-PRESSURE TYPE METERING CONTROL 3 Sheets-Sheet 1' Filed Oct. 11 1945 PIC-3.5

n a n ln w A m E F 7/ A. w kl FIG. 7 FIG. a

FIG. 2

INVENTORS SIDNEY .1. SHAMES WALTER J. RALEIGH ATTORNEY FIG.!

Aug. 16, 1949. 5. J. SHAMES ETAL ANIFoLD-PfiEssURE TYPE METERING CONTROL Filed Oct. ll, 1945 3 Sheets-Sheet 2 INVENTORS SIDNEY J. SHAMES WALTER J. RALEIGH ATTORNEY Aug. 16, 1949.

5. J. SHAMES' ET AL.

MANIFOLD-PRES SURE TYPE METERING CONTROL 3 Sheets-Sheet 3 Filed Oct. 11 1945 II IIIIIII INVENTORS SIDNEY J. SHAMES WALTER J. RALEIGH ATTORNEY Patented Aug. 16, 1949 Sidney J. Shames, Cleveland, Ohio, and

Walter J. Raleigh, St. Paul, Minn.

Application October 11, 1945, seamen; Y

6 Claims. (01. 236-79) (Granted under the act of ,March 3, 1883, as amended April so, 1928; 310 0. G. 757

This invention relates to a manifold-pressure type automatic metering control and especially to a device for automatically controlling the rate of fuel flow to an internal combustion engine.

The present device is designed to automatically actuate the capacity control of the fuel-injection pump, which in turn delivers fuel through injec tion lines and nozzles to each of the individual engine cylinders or intake pipes in accordance with the mass rate of air flow to them. The engine for which the proposed control is used is one in which the charge is ignited by an electric spark and in which the charge must have definite fuel-air proportions. V

The purpose of this invention is to maintain predetermined proportions of fuel flow to air flow into the'engine, independent of the altitude and power at which the engine is run, taking into account the volumatic efficiencies of the engine and of the fuel injection pump; thus providing for fuel-air mixture control at any engine speed and air flow.

The existing fuel injection systems that use a venturi for measuring the air flow and proportioning the fuel delivery to an engine encounter dimculties and disadvantages in that the venturi :imposes a restriction in the intake air line that results in a loss of critical altitude of the aircraft engine, and the venturi cannot proportion the fuel delivery with the desired accuracy, for if it were made small enough to proportion satisfactorily at low air flows, it would impose too great a restriction at high air flows, requiring that a compromise design must necessarily be selected with the result that greater metering tolerances must be permitted than are desirable.

Various existing fuel injection systems other than a venturi have been used for measuring air flow and proportioning fuel flow to an engine, but none of these have been entirely satisfactory.

An object of this system is to provide for rich and lean operation in cruising, for enrichment under high power take-off conditions and for adjustable mixture ratios in the idling range;

Another object is to provide a system which. will account for engine air flow under all conditions of engine operation, and thus maintain constant fuel-air ratios under varied engine operating conditions.

By providing for varied mixture ratios, the

. element;

metering system protects the engine against overheading, misflring, bacltfiring, etc., under all conditions of engine operation and, in addition, pereconomical operation in the cruise range which is necessary with long-range aircraft.

The features of this invention are described in connection with the accompanying drawings.

Figure 1 shows the required operating conditions that a system must provide;

Figure 2 is-an obliquely sectioned view of the mechanism;

Figure 3 is a sectioned view of the idling adjustment;

Figure 4 shows the joint between the directing lever and the piston shaft;

Figure 5 shows the joint between the pilot lever and the flexible rod;

Figures 6, '7, and 8 are views of the hinge joint; Figure 9 shows the pin used with the hinge joint; Y

Figure 10 is a detailed sketch of the bellows device, showing its connection to an engine;

Figure 11 is a sketch of a bellows device with a bi-metallic temperature compensation element;

Figure 12 is a sketch of a bellows device with a hydraulic capsule temperature compensation Figure 13 is lever system; L V

Figure 14 is a right-angle projection of Figure 13; and

Figures 15 lever system. I H p In Figure 1, abscissaA represents air flow to the engine in, pounds per hour and ordinate B represents fuel-air ratio. Distance" C-D along abscissa A represents the air flows under idling conditions, D-E under cruising conditions, E-F under higher power conditions, .and F-.G under take-off conditions. Curve Hrepresents the air flows and fuel-air ratios required with operation of the metering controlin the fautomatic rich setting, whereas ,curve I represents the conditions a kinematic diagram of the servoand 16 show a variation of the servofor the automaticlean setting. Curves J and mixture ratios shown.

' The air consumption of an engine can be represented as a continuous single-valued function of the absolute intake-manifold pressure, absolute exhaust back pressure, absolute intake-manifold temperature, and engine speed. Mathematically, the relation can be stated as follows:

Pm, absolute intake-manifold pressure Pe, absolute exhaust back pressure Tm, absolute intake-manifold temperature N, engine speed This equation takes into account the air flowing to the engine under all conditions of engine operation; that is, power, speed, and altitude. The relation between these variables is experimentally determined by operating the engine under varied operating conditions. The equation so determined can then be appliedto all engines of a given design.

In the subject control system, pressureand temperature-sensitive units are combined to produce a displacement that is proportional to the absolute intake-manifold pressure, the absolute exhaust back pressure, and the intake-manifold temperature in accordance with the preceding experimentally determined relation of these variables to engine air flow. By means of a hydraulic servosystem, this displacement is magnified and caused to actuate the capacity-control lever of the fuel-injection pump. The design of the hydraulic servosystem is such that a change in magnification of movement is possible, the system being similar to asimplelever system with a movable fulcrum. Once a multiplying ratio is selected, this ratio will be maintained for all air flows. This method of control enables the system to maintain two definite fuel-air ratios, rich and lean, in the cruise range. Mixture enrichment for increased power and take-off operation is provided by'interposing a cam between the servopistonshaft and the capacity-control lever of the fuel-injection pump. This cam also permits introduction of a multiplying factor in the linkage system and therefore provides for through a slot (not shown) similar-to slot 1.

Trunnion 6 causes lever 5-to follow movements of shaft 4 with norestraint, rotatively or axially, of said lever by said shaft. Lever 5, being thus acted upon and being subjected to considerable restraint at bearing 8 ue to'resistance on piston shaft 9 of entrapped oil in cylinder l acting on piston H, is caused to move in the direction of action of shaft 4, pivoting about trunnion 8 and causing a corresponding motion of the end of pilot lever l2. Lever I2 is connected to lever by means of special spherical bearing l3, said bearingbeing slidably and rotatively mounted on both levers l2 and 5 so as to eliminate binding or undesirable restraint ofsaid levers. Lever l2,

being caused to move as described and having as its fulcrum pivot bearings I4, reverses and transmits to pilot valve I6 the motion imparted to it bearing 25 which is fitted in slot 26a.

at its connection with lever 5. This motion is transmitted to pilot valve it through flexible rod II which accommodates alignment difierences between bearing and the extended line of motion of pilot valve l6. Pilot valve l6 being thus displaced by action of bellows device 2 on the lever system just described admits oil under pressure from channel 8 to channel l9 or i 2!), simultaneously connecting those channels not connected to said high-pressure channel I8 to low pressure channel 2i or 22. This'action results in a pressure difference on opposite sides of piston ll causing it to move in the direction of lowest pressure. Fulcrum pivot bearings I4 are mounted on stub 5% attached to plate 5|. Plate 5! is rotatable about the collar 52 secured to the metal case axially with the valve l6. Lever 53 connected to a handle not here illustrated turns shaft 54 having crank 55 engaged by pin 56 fixed in plate 5|, and adjustment of the lever 53 imposes a change in the positioning of fulcrum is with respect to the point of connection to the directinglever 5, this acting to vary the distance of bearing l3 from the trunnions 6 and B and to therefore vary the resultant motion of the piston H and the dependent fuel flow. l

Piston H, being thus caused to move by the action (through the described lever system) of bellows device 2 on pilot valve 16, is arrested in its motion by the restoration through said lever system of pilot valve 5 5 to a position where lands 23 til pilot valve Ifi is moved by action of bellows devices 2 and 36 on the lever system as described, or by other means. Movement of bellows 2 thus produces definite predictable amounts of motion of piston shaft 9 by moving shaft 4. The magnitude of these motions is proportional in a constant ratio dependent on the distances of bearing l3 from'trunnions 6 and 8, respectively. A detailed discussion of the means of attaining this proportional relationship is given in succeeding paragraphs.

The controlled movement of piston ll actuates cam plate 26, through piston shaft 9, and ball Cam plate 26 is mounted on ball bearing 21 fixed in case I so that the sliding action of piston shaft 9 causes cam plate 26 to rotate about bearing 21. Power-delivery shaft 30, which is mounted in case I and connected to quantity-control lever 33 of engine fuel-supply device 38 through link 32, is actuated by cam surfaces 28 to which ball bearing 29 is fitted. Ball bearing 29 is also attached to shaft 31!. The position and curvature of cam surfaces 28 can be varied in their manufacture to attain an infinite range of motion relationships between power-delivery shaft 30 and piston shaft discharged through exhaust pipe 4!. Pitot tubes 34a and 35a are arranged to circulateair-from inlet pipe 40a through inlets 3,4 and 35 and through the bellows compartment in case I, and to maintain in said chamber at all times the same absolute pressure as exists in inlet pipe 40a.

Bellows unit 2 consists of flexible bellows 2.

mounted on chamber 20 which in turn is fastened to bellows 36. The other end of bellows 361s fastened to rigid strut la. Shaft 4 is so attached to the free end of bellows 2 so that as the pressure is increased in the bellows compartment both bellows move to the right against springs 2b and 36a or, as the pressure in the bellows compartment is reduced, conversely move to the left.

Bellows 2 is sealed and filled with an inert gas, the pressure of which increases, causing the heel? lows to expand, when the temperature in case I is increased in accordance with thetemperature of air circulated toit from engine inlet pipe Mia. The magnitude of response to changes in inletair temperature is determined by the pressure and temperature of the gas charge of bellowsl at the time of sealing. Chamber 20 provides additional volume for this gas and reduces the volume change error due to the expansion and con traction of bellows 2 to an insignificant amount. Strut l a eliminates the error due to the thermal expansions of case I and bellows '2 and 36, thus making the assembly responsive solely to the temperature of the gas in the gas-filled bellows 2.

Bellows 36 is so arranged that its internal pressure follows the exhaust back pressure by means of communicating line 31. By this arrangement, exhaust back pressure affectsthe movement of bellows 3B in a manner opposite to the inlet-pipe pressure, corresponding to the opposite effects of exhaust back pressure and'inlet-pipe pressure on air quantity flowing through the engine. The relative magnitudes of these efiects on them'ovement of the free'end of the'bellows assembly are determined by the relative sizes of bellows 2 and and springs 2b and 36a. It is seen then that the relative influence of inlet-air pressure, inletair temperature, and exhaust back pressure on the magnitude and direction of motion of the free end of the bellows assembly can be predetermined- This predetermination makes possible the construction of a bellows unit that produces a mechanical movement in accordance with changes in air flow as defined by the experimentally deter-.- mined mathematical relationship between the parameters (inlet-air pressure, inlet-air ternperature, and exhaust back pressure) given 'previously. 7

Several alternate arrangements for causing the bellows unit to move in response to temperature changes have been considered. One method .consists of the application of a. bimetallic device in the space occupied by the volume chamber 20. Figure l I shows bimetallic device Zdattached between bellows 2 and 35. An increase in tempera ture causes bimetallic device 201 to increase its length along the axisof bellows 2 and 36 by the well-known principle of warpage of joined 5 metals of unequal temperature-expansion rates. Another method of obtaining a mechanical movement of the bellows unit through .a change in the air temperature of the engine inlet is to provide a hydraulic-capsule unit between the bellows units shown in Figure 12. Capsule 2c, of small volume, is connected by capillary tube 2 to a bulb 2g, of relatively large volume, placed in the engine inlet pipe 4611. This system is charged with a volatile liquid that produces an increase in pressure within capsule 2e when the temperature of the bulb 2g is increased. Capsule 2e expands because of the increased internal pressure and produces a movement along the axis of the bellows assembly in accordance with the temperature of bulb 2g, which is immersed in the engine inlet air. 7

- Bimetallic device 2d or hydraulical-capsule unit 26 can be arranged in any position that causes the proper direction and magnitude of motion of a air flow (Fig. 2), as explained above, and move bellows shaft 4 upward, so piloting the servomechanism that the fuel supply is thereby reduced. The rate of elongation of the bellows due to lower rates of air flow is decreased by causing spring Ad in the idling device of Figure 3 to act against the elongating bellows. This action is accomplished by providing lug 4a (Figs. 2 and 3) extending from bellows shaft 4. Lug 4a comes in contact with pin cf as lug 4a moves upward; sleeve 48 is moved upward also, for it is connected to pin 41 by screw threads; Sleeve 4e has an extension shou der that carries sprin 4d and that, being restrained by extension ib of case I, is thus compressed by the upward movement of the assembly of sleeve ie and pin 41. Spring 4d thusacts against the expanding action of bellows 2, reducing its rate of expansion as the engine airflow rate diminishes in the idling range and. en riching the fuel-air ratio.

The initial tension of spring M is controlled by threaded ring 49. If this initial tension exceeds zero, the upward motion of bellows 2 and 36 is arrested until a certain decrease of air flow occurs. The rate of fuel delivery to the engine remains'constant during the range of this airflow decrease, causing an abrupt enrichening of the mixture. By adjusting threaded ring 49, the magnitude of this range may be regulated to desirable amounts.

The range of travel of spring 411 is limited by threaded ring 4c, the position of which is adjustable with respect to bellows-actuated sleeve 46. Such adjustable limitation of the bellows travel is desirable to fix the minimum rate of fuel flow to, the engine. r

The rate of air flow at which the idling device described above commences to act is adjusted by screwing threaded pin 4 into or out of sleeve 4e, thus affecting the amount of movement of bellows-actuated lug 4a before contact with pin 4 occurs.

Figure 4 shows details of the joint between directing lever 5 and piston shaft 9 of Figure 2.

The purpose of this joint is to eliminate lost motion between the connected parts, thus contributing to the accuracy of response of the servomechanism, and also to allow accidental rotation of the piston shaft without straining the lever system. A block W is fitted over piston shaft 9 (Fig. 4) and is held against conical surfaces c by springSb, secured by pin 9d. Spring 9b is of such tension as to maintain contact at conical surfaces 0 under all upward loadings encounteredin normal operation, but not to load surfaces 0 in excess of this amount; it permits rotation of shaft 9 on block but with a minimum of. friction. Trunnion shaft 8 extends from either side of block 9a and is engaged by V-cut extensions 5a of lever 5. Links 50 connect trunnion shaft 8 to cross pin 5d, which is arranged crosswise of lever 5 in slotted holes 5e. Spring 51) acts between securing pin 5 and cross pin 5d, holding v-cut extensions 5a against trunnion shaft 8 with a force just sufficient to prevent separation under normal loads.

Figure 5 shows details of the joint between pilot lever l2 and flexible rod ll of Figure 2. The purpose of this joint is to eliminate lost motion between the connected parts, thus contributing to the accuracy of response of the servornechanism. The end of pilot lever i2 is forked and plate Ila on the end of rod I'I fits loosely into this forked part. Pin [5 is pressed tightly through a hole in plate Ma and forms trunnions that rest in V-cuts I20 on fork projections of pilot lever I2. Flat spring l2a is fastened. to pilot lever l2 by means of screws I212. The design of the whole is such that fiat spring i2a holds pin l5 against V-cuts [2c of pilot lever l2 with a force sufiicient to prevent lost motion under load but not sufiicient to cause undue friction in rotation of said pin.

Figures 6, '7, and 8 show details of a special joint employed between shafts 3t and 32 of Figure 2. This device provides in shafts 38 and 32 a hinge joint with a removable pin that is dependably locked in position; said pin is easily removed for disassembly of the shafts, and said pin and locking device are contained within the perimeter of the shaft cross section. In Figures 6, 7, and 8, extension 32a of shaft 32 fits into slot 38a of shaft 30. Pin 3| passes through these two parts and has a hole through its center in which locking pin 3|a fits. Locking pin tia is made of moderately soft metal preformed with one end as shown in Figure 9. As shown in Figures 6 and 7, grooves Silb on the outside of shaft 39 radiate from the center of pin 3i, being cut in pin SI also, and are of a depth slightly greater than the thickness of locking pin 35a. When the joint is assembled, preformed locking pin 3la is placed in position through pin 3! with its bent end fitting in the bottom of groove 3% on one side of shaft to; the other end is then bent into position in the bottom of the corresponding groove on the opposite side of shaft to with pliers or by hammering. When locking pin am is preformed to the shape shown in Figure 9, the lengths of the portions on either side of the band are made so that after the pin is installed in the joint, both ends project about half way across grooves 380, which are cut crosswise of grooves 382) and are a little wider and deeper than grooves 36?) in order to accommodate a screw driver or flat tool to facilitate unbending locking pin 31a for disassembly of the joint.

Figure 13 is a kinematic diagram of the servo lever system, and Figure 14 is a right-angle projection of Figure 13. This system consists of a lever DF, connecting hinge points D, E, and F, which at one limit of its motion is on the line XX; another lever DH which joins lever DF' at D at an angle FDH (Fig. 14) and has a fulcrum at G; a bellows device A which is mounted on a shaft joining it to lever DF at E and which causes motion of point E along YY (Fig. 13); a piston B which is mounted on a shaft connecting it to lever DF at F so that motion of point F is restricted to line ZZ parallel to YY. Pilot valve C controls the flow of oil through ports N1 and NZ to either side of piston B from inlet and away from said piston to outlets P1 and P2. Pilot valve C is joined to lever DH at H so that, when said lever rocks on fulcrum G, pilot valve C is caused to slide along line QQ. Any motion of point D that causes such rocking of lever DH will cause sliding action of pilot valv C. Junction D of levers DF and DH may be moved along line XX, as'from D1 to D2 without causing movement of pilot valve C, inasmuch as point H and motion path GIGZ of fulcrumG (Fig. 14) lie in a common plane with line XX at the neutral position of pilot valve Ci.

When the lands M1 and M2 on pilot valve C cover ports N1 and N2, oil cannot flow to or away from piston B and piston B is thereb locked stationary. (Lands M3 and M4 act as seals.) This position of pilot valve C is termed the neutral position. The action of piston B is controlled by bellows A through the linkage described above in the following sequence: Bellows A moves point E to any position E, causing lever DF to assume position D'iF and lever DH to assume position DiH'. Pilot valve C is moved upward (Fig. 13) by the amount I-IH', connecting oil inlet port 0 to port N1 and to upper side of piston B and connecting oil outlet port P2 to port N2 and to lower side of piston B. Oil pressure then acts downward on piston B causing point F to be moved to F1. Lever DF is thus caused to rock on point E so that point D'1 moves upward to point D1 on line XX at which position pilot valve C is restored to the neutral position, thus arresting motion of piston B as explained above. Bellows motion EE' has thus resulted in piston motion FFi. The mangnitudes of these motions are proportional to each other in the ratio DiE to DlF inasmuch as triangles DiEE' and. DiFFi are proportional because lines YY and ZZ are parallel. These proportional triangles will always exist in operation of the control because at equilibrium conditions point D always returns to the same position on line XX. Through this proportional characteristic, a small motion of bellows device A, corresponding to changes in air' flow to the engine, may be converted to larger motions of piston B to control the quantity of fuel delivered to said engine with a constant ratio between the magnitudes of said motions.

Adjustment of the motion ratio between bellows A and piston B is obtained by moving point D along line m as described previously. The ratio of motion FFi/EE is thus decreased to FFz/EE' by moving point D from D1 to D2 and vice versa.

Figures 15 and 16 show a variation of the system described above. This variation provides a means of reducing the ratio of the piston-bellows motion from the maximum value provided in the dimensions of the system to zero. Such a reduction may be desirable on the subject control to enable the operator to cause the servomechanism to cut 011' fuel delivery by moving the lever provided for the control of the fuel-air ratio.

In Figures 15 and 16, corresponding points are lettered in a manner similar to Figures 13 and 14. The principal difference in the two systems is that the intersection point D between DF and DH is placed on lever DF between point E, intersec tion of this lever with the bellows shaft, and point F, intersection of this lever with the piston shaft. The triangles EEDi of bellows motion and FF1D1 of piston motion, formed by the intersection of the straight lines XX and DFi, are similar, becouse EE' and FFI are parallel. Point D is always on line XX at equilibrium conditions as in the system of Figure 13, thus, for any posiassists tion of patents-max: between the limits E and F, these proportionalemotion triangles occur.

' Pistonmotion inwthis servosystenf is in opposite direction to bellows motion; As point Dnioves toward F the ratio. of piston motion to bellows motion approaches zero,with acorresponding decrease in the setting of the quantity-control lever, so that when points D and-F are coincident, the

piston locatesitself at the lower limit of its stroke regardless of the position of the bellows.- ,This position of-the pistoncauses the'quantity-control lever'of the fuel-supply-appar'atus to beset at a minimum or zero fuel delivery. Point D is caused to become coincident with point F by swinging lever DH about center H on axis QQ. (See Fig. 16.) Fulcrum G of lever DH swings on arc GIGS during this motion.

The control system described'herein requires that the fuel-injection pump have a speed-delivery characteristic similar to the air-fiow-speed characteristic of the engine on which it is to be used. This requirement is necessary in order to account for changes in air flow due to variations in engine speed, inasmuch as such changes in air flow require corresponding changes in fuel flow in order that constant mixture proportions may be maintained. The required speed-delivery characteristic can be obtained by suitable modifications of the fuel-injection pump, lines, and

nozzles; that is, if these parts are suitably designed, the variation in fuel flow with speed at a constant setting of the pump capacity-control lever can be made similar to the variation in engine air flow with speed at a given set of the values of the three variables, intake-manifold pressure, intake-manifold temperature, and exhaust back pressure. By the use of a suitable pump speed-delivery characteristic, the control thus takes into account all the variables in the experimentally determined engine-air-flow equation.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

Having described our invention, we claim:

1. In a fuel-metering device, the combination of a housing, a hydraulic cylinder and a piston reciprocable therein mounted on said housing, a pilot valve connected to said cylinder for control of fluid flow to either end of said cylinder, a shaft connected to said piston having at one end a connection to the quantity control means of a fue1supply system, a main lever attached at one end to the other end of said shaft and fulcrumed at midlength to the end of a second shaft attached to means responsive to changes in pressure and temperature of a medium, a second lever attached at one end to said pilot valve and fulcrumed substantially midlength on a stub movable on said housing, said levers swivelled together at their other ends by a joint slidable on either lever, whereby said piston and connection attached thereon is movably responsive to changes in pressure and temperature of said medium, and said pilot valve is centered in neutral position after each piston movement.

2. In a fuel-metering device, the combination of an element responsive to changes in pressure and temperature of a medium, a quantity control element'on a fuel-supply system, and means connecting said pressure and temperature responsive element with said quantity control element, said means comprising a hydraulic cylinder, a piston V of an element respon'si Pic l.

in said cylinder, a pilot valve for controlling flow of fluid to opposite facesof said piston, a shaft connected to said plst on',11a lever pivotally attached'to one end of said shaft and connected to said pressure and temperature responsive elemerit, a second leverswivelled atone end to said first lever and at'the otherto said pilot valve, and a movableiful' crum supporting said second lever whereby the effectivelengths of saidlevers ma be varied to change thefope'rable. setting of said piston and associatedquantity control element.

3. Ina fuel-mete'ri'n device; the combination }to changes in pressure and temperature of edium, a control arm of a fuel supply; system andmeansconnecting said element with said control arm comprising a cylinder, a" piston"reciprccable'insaid cylinder, a pilot valve for controlling the flow of hydraulic fluid to either face of said piston, a shaft drivably attached to said piston and mechanically connected to said control arm, a lever pivotally engageable with said shaft fulcrumed on said element, a second lever shiftaloly fulcrumed on a housing enclosing said element and attached to said pilot valve for operation thereof, said levers adjustably connected together at their free ends where- :by movement of said element in response to pressure and temperature changes is transmitted to said pilot valve for control of fluid to said piston and said control arm connected thereto, said pilot control adapted to return to neutral at positions of rest.

4. In a fuel-metering device, the combination of an element responsive to changesin pressure and temperature of a medium, a fuel-supply device and means piloted by said element for controlling said fuel-supply device comprising a cylinder, a piston in said cylinder, a pilot valve for controlling the flow of fluid to opposite sides of said piston, a shaft connected to said piston, a lever pivoted at one end to the upper end of saidshaft and connected at midlength to said element, a second shaft pivoted intermediate its ends to a movable stub and operatlvely connected at one end to said pilot valve, said levers being connected to each other at their other ends by a swivelling joint slidable on each lever, said first lever pivoted to said shaft by a lost-motion free joint having a conical surface and matching surface rotatably held together by a spring.

5. In a fuel-metering device, an element responsive to changes in pressure and temperature of combustion air, a fuel-supply device and means piloted by said element for controlling said device comprising a cylinder, a piston in said cylinder, a pilot valve for controlling the flow of fluid to opposite sides of said piston, a shaft connected to said piston, a lever connected at one end to said shaft and pivotally mounted on said element, a second shaft fulcrumed at its midlength to a movable fulcrumand connected'at one end to said pilot valve and at the other to said first lever, one end of said shaft operatively connected to a cam which operates a quantity control mechanism of said fuel-supply device, said connection to said cam being a hinge joint having a removable tubular pin with a special lock wire axially se- 7 curing said pin in said joint, ends of said wire besense.

11 controlling the flow ofhydraulic fluid to said cylinder, a pair of levers joined together at their ends by a hinge slidable on each lever, one of said levers fulcrumed on said pressure. and temperature responsive device and pivotally connected to said piston, the other of said levers fulcrumed on a stub movably mounted on said housing and connected to said valve, whereby movements of said pressure and temperature responsive device actuate said valve to admit fluid to said cylinder and move said piston a distance proportional to the efiective lengths ofssaid levers.

V SIDNEY J. SHAMES.

WALTER J. RALEIGH.

REFERENCES CITED The following references are of record in the file of this patent:

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